1. Field of the Invention
This invention generally relates to accessing remote memory with low latency by using the Non-Volatile Memory Express (NVMe) protocol over a network.
2. Description of the Related Art
Typically, a CPU can access remote memory or I/O devices over a network by using network protocols. One conventional approach to access remote memory or I/O devices is through iSCSI storage. This approach uses significant processing by the CPU, which increases total access latency. Accessing remote memory or I/O devices via iSCSI storage usually has latency four to five times greater than a direct access of local memory or I/O devices. This leads to noticeable performance and throughput degradation for systems requiring remote memory or I/O devices access over a network.
A relatively new interface standard that deals with local non-volatile memory access is NVM Express (NVMe), sometimes referred to as the Non-Volatile Memory Host Controller Interface Specification. NVMe is a register-level interface that allows host software to communicate with a non-volatile memory subsystem. This interface is optimized for enterprise and client solid state drives (SSDs), which is typically attached to the PCI Express (PCIe) interface. NVMe provides a direct I/O access to local non-volatile memory. Using NVMe, the latency of read and write operations is reduced, compared with connecting over traditional I/O interfaces, such as SAS (Serial SCSI) or SATA (Serial ATA).
However, NVMe has a limitation pertaining to passing of data over Ethernet switches or other types of networks. Generally, NVMe is designed to access local SSDs and is not defined in terms of accessing remote storage through a network. NVMe as defined today does not provide solutions for accessing multiple remote SSDs by multiple host CPUs through a network. Accordingly, there is a need to enable NVMe to work efficiently over a network (e.g., Ethernet network) for accessing remote SSDs and name spaces over the network.